This application relates to a sports racket of the type used in a game such as tennis, racket ball or squash.
Players of racket sports such as tennis, racket-ball and squash sometimes develop arm and elbow disorders because of the effect of the vibration of the racket during play. The sports rackets are strung under tension and upon some conditions of ball impact, an objectionable vibration is transmitted from the strings to the racket frame and, via the racket frame, to the arm of the player, to cause a complaint commonly referred to as tennis elbow.
Modifications to racket designs have been tried in the past, to reduce the magnitude of the vibrations transmitted to the am of the player and thereby reduce the risk of injury. They have not proved wholly successful.
One modification taught by the prior art is shown in U.S. Pat. No. 1,250,329. That patent teaches the mounting of a resilient foam material between the strings of the racket under compression. This has some dampening effect on the vibration but most of the vibration is still transmitted to the player and it continues to be a problem.
Another type of racket modification is taught in Taiwanese patents 27535 and 120748. These patents disclose a discontinuity in the rim of the frame to provide spaced apart free ends and the filling of the space between the free ends with a hard plastics material plug that is secured in position by the racket strings. The arrangement does permit relative movement of the free ends of the frame but only in a direction substantially at right angles to the plane of the rim. This arrangement does absorb some of the shock of a poorly hit ball that would cause excessive vibration to be transmitted to the arm. However, it is not a very satisfactory answer. There is still objectionable vibration transmitted to the arm of the player. Further, the relative movement of the ends of the frame and the insert causes an objectionable noise. In several years of use and availability, the design has not been well received by players and the problem that it was intended to solve continues.
The present invention provides an insert of similar geometric proportions to the one of the Taiwanese patents but it is made of a resilient material that permits movement of the free ends of the frame at the discontinuity in a direction with a component substantially towards each other as well as in a plane substantially at right angels to the plane of the racket. This more free movement of the ends as they compress the resilient insert under conditions racket vibration results in the absorption of substantially more of the vibrations from impact of the ball and racket than the prior construction and is important in reducing vibration of the type that causes tennis elbow. The resilient insert also avoids the objectionable noise of the rigid plastics insert.
The present invention also provides an improved means for transmitting movement of the strings under conditions of excessive ball impact to the insert to further improve the operation of the racket.
It is an object of the present invention to reduce the vibration of the racket caused by the impact of the playing ball so that fewer players develop arm problems.